The invention can find application at automobile, sanitary-engineering, electrical-engineering, mechanical-engineering and some other plants, wherein large-scale or mass production is practised.
Known in the present state of the art is a method of making mould cores from flowable sand mixtures, consisting in that the flowable mixture is pressure forced into a pre-heated core box, whereupon the box is sealed tight and the mixture is allowed to stand therein for a lapse of time enough for the mixture to solidify after which the box is opened and the finished core is taken out of it (cf., e.g., U.S. Pat. No. 3,802,484).
Said method is instrumental in making any cores (preferably band-shaped cores) as a whole as a natural vent hole or porosity is formed inside the core in the course of solidification, through which gas venting can occur efficiently.
Known at present is also a machine for making mould cores from flowable sand mixtures in hot multiple core boxes, which carries said method into effect.
The machine incorporates a supporting frame whereon are arranged as along the run of the core production process cycle: a sand mixture preparation mechanism, a mechanism for pressing said mixture in core boxes, a mechanism for splitting up the core boxes and a mechanism for discharge of finished cores. Said supporting frame carries also a means of conveyance of the core boxes along the run of the core production process cycle whereon the core boxes are placed. Each of the core boxes has a top piece and a bottom piece, the former piece having central and peripheral core print openings. Provision is also made in the machine for a gate situated on the top piece of the core box so as to interact with an individual drive made fast on the supporting frame at the pressing mechanism in order to close the central core print openings, and with another individual drive made fast on the supporting frame before the splitting-up mechanism so as to open the central core print openings. The machine comprises also a means adapted to shut up the peripheral core print openings in the core boxes (cf., e.g., USSR Inventor's Certificate No. 509334).
In the afore-discussed machine the means for shutting up the peripheral core print openings is made as heated plugs.
The afore-discussed machine incorporates a rotary wire brush arranged before the splitting-up mechanism.
The machine operates as follows.
The original constituents of the sand mixture are fed to the mixture preparing mechanism. The thus-prepared flowable sand mixture is delivered to the pressing mechanism, wherefrom the mixture is forced into a preheated core box through its central core print openings. When the mixture is pressed into the box the peripheral core print openings are shut up with heated plugs which contributes to an efficient growth of a solid skin at the ends of these openings. Pressing of the mixture having been over the core box is allowed to stand for a while, whereupon the gate shuts up the central core print openings after having been actuated by an individual drive, and the core box is transferred by the conveyance means to a next technological station. While being transferred to that station the top piece of the core box is cleaned of the mixture remainder with the rotary brush. Then another individual drive turns the gate to open the central core print openings, the core box is split up, the finished cores are taken out of it and are carried away from the core box zone by the core discharge mechanism. Next the core is reassembled and returned by the conveyance means for a next sand mixture pressing operation. Thus, a whole cycle is repeated.
In the machine under discussion, in order to provide a solid skin of a required thickness at the ends of the peripheral core prints, it is necessary to substantially prolong the time of contact of the mixture with the heated plugs which results in an increased stay time of a core box at the station of the pressing mechanism and hence in a reduced output of the machine.
Furthermore when cleaning the top piece of the core box from the remainder of the mixture with the rotary brush, it is fraught with a danger of damaging the already formed skin at the exposed ends of the peripheral core prints, or even breakage of said skin with the spoiled cores as a result.